modern hominoids in growth pattern of the cranial cavity, a figure between 

 95 and 98 per cent, say 96.5 per cent, or the mean for both sexes, 95.5 

 per cent, would probably give a realistic assessment of the adult capacity 

 that the type specimen of H. habilis had attained at the time of the 

 individual's death. This figure may err somewhat on the conservative 

 side, in view of the relatively low value (93 per cent) cited by Ashton 

 and Spence for man; on the other hand, Schultz's figure for human 

 males is higher (97 per cent). It should be recalled that the figures of 

 95.5 and 96.5 per cent are based upon intermediate categories, possibly 

 including individuals both dentally younger and dentally older than the 

 H. habilis type specimen. 



The mean between the male and female averages for the 4 hominoids 

 is 96.5 per cent according to Schultz, while the combined-sex mean for 

 the same 4 hominoids is 95.5 per cent according to Ashton and Spence. 

 The intermediate value of 96 per cent would seem to be a not unlikely 

 estimate of the probable percentage of adult capacity attained by the type 

 specimen of H. habilis, without begging the question as to its sex. 



The "adult capacity" of Olduvai Hominid 7. If then we assume that 

 at 657 c.c. the endocranial capacity of H. habilis was already 96 per cent 

 of the adult value, the adult value would have been 684 c.c. We are back 

 where we were, close to the upper part of the original 2 central estimates 

 for H. habilis type (675 and 680 c.c), only with much greater confidence 

 in the validity of our estimate. It is proposed, therefore, that we accept 

 the figure of 684 c.c. as the "adult value" for the type specimen of 

 H. habilis. 



Thus, in relation to my estimate of the mean for A. africanus (494 c.c), 

 the "adult" of H. habilis type shows an excess of 190 c.c, or 4.58 S.D.s. 

 In relation to Robinson's estimate of the mean for A. africanus (430 c.c), 

 the "adult value" of H. habilis type shows an excess of 254 c.c. This is 

 equivalent to an excess of 6.12 S.D.s by my estimate of the S.D. (41.5 c.c) 

 and of 5.08 S.D.s by Robinson's estimate of the S.D. (50 c.c). All 3 values 

 for standardized excesses of the H. habilis type "adult" capacity over the 

 mean for A. africanus exceed the greatest standardized excesses tabulated in 

 Table 12.* 



* [n relation to Holloway's mean of 442 c.c, the adult value of 684 c.c. is 242 c.c. in excess, which, 

 according to an S.D. of 2159 c.c, is equivalent to an excess of 11.21 S.D.s. In comparison with my 

 modification of Holloway's mean (450 c.c), the adult value for Old. Horn. 7 is 234 c.c in excess, 

 which, according to an S.D. of 22.49 cc - ' s equivalent to an excess of 10.40 S.D.s. 



71 K 



